Carhart Notch
Pronunciation: KAR-hart notch
A characteristic dip in bone-conduction thresholds at 2000 Hz seen on the audiogram of patients with stapes fixation, particularly in otosclerosis.
Full Definition
The Carhart notch is a mechanical artefact observed on the bone-conduction audiogram at 2000 Hz (sometimes also at 500 Hz, 1000 Hz, and 4000 Hz) in patients with stapes fixation due to otosclerosis. It does not represent true sensorineural loss but rather reflects reduced resonance of the ossicular chain when the stapes is immobile. The notch typically resolves following successful stapedectomy surgery. Editors must understand that the Carhart notch is a clinical sign observed on an audiogram, not a disease or condition in its own right. It should always be referred to in conjunction with its audiometric context and not confused with noise-induced hearing loss, which produces a different notch pattern, typically at 4000 Hz.
Usage
Usage note: Always capitalise 'Carhart' as it is an eponym. Clarify in clinical documents that the notch is a mechanical artefact, not indicative of true cochlear damage.
In Context
- "The Carhart notch was clearly identifiable at 2000 Hz on the bone-conduction audiogram, supporting the clinical diagnosis of otosclerosis." — Audiological assessment report
- "Post-operatively, the Carhart notch had resolved, indicating successful restoration of ossicular mobility." — Surgical outcome report